In a one-component room temperature vulcanized silicone sealant system, each component has a crucial impact on performance: the relative molecular mass of the base polymer will affect the fluidity, process operability and performance of the sealant. Adhesion properties; the functional groups and functionality of the cross-linking agent will affect the adhesiveness and cross-linking speed of the sealant; the type and amount of fillers will affect the strength, process operability and thixotropy of the sealant; the catalyst will affect the sealant vulcanization speed and storage stability.
As a tackifier, a small amount of silane coupling agent can significantly improve the adhesion of the sealant to the base material. However, for different base materials, it is still necessary to choose the appropriate silane. Only the type of coupling agent can achieve the expected bonding effect. Chemical Engineering studied the effects of two silane coupling agents, KH-560 and KH-792, on the performance of one-component room temperature vulcanized silicone sealant.
Preparation of one-component room temperature vulcanized silicone sealant
Add a certain amount of 107 glue, dimethyl silicone oil and calcium carbonate into a high-speed mixer , heat to 100~130 ℃, vacuum and stir for 120 minutes to remove the moisture in the filler; after the base rubber cools to room temperature, add cross-linking agent, chain extender, catalyst and coupling agent in different proportions in sequence (Table 1 ), and stir evenly under vacuum to obtain a one-component room temperature vulcanized silicone sealant.
The effect of silane coupling agent ratio on the adhesive properties of sealants
Preparation Using different silane coupling agents, the effect of the obtained one-component room temperature vulcanized silicone sealant on the bonding performance of uncoated, colorless, transparent float glass and anodized aluminum was investigated. No matter what coupling agent ratio is used, the one-component room temperature vulcanized silicone sealant has little effect on the adhesion of the glass, and the failure mode of the sample is 100% cohesive failure.
When the amount of KH-560 is not less than KH-792, the one-component room temperature vulcanized silicone sealant has poor adhesion to anodized aluminum, and the failure mode is mixed failure; as KH- As the dosage of 792 increases, the adhesion of the one-component room temperature vulcanized silicone sealant to anodized aluminum increases, and the failure mode changes to 100% cohesive failure. When choosing aluminum as the base material, the one-component room temperature vulcanized silicone sealant with high KH-792 content has better bonding effect.
The effect of silane coupling agent ratio on tensile modulus of sealant
As the dosage of KH-792 increases, the tensile modulus of the one-component room temperature vulcanized silicone sealant first increases and then levels off. When the proportion of KH-792 exceeds 66.7%, the tensile modulus tends to be stable.
The effect of silane coupling agent ratio on the elongation at break of the sealant. As the amount of KH-792 increases, the elongation at break of the sealant gradually increases.
The proportion of silane coupling agent in the one-component room temperature vulcanized silicone sealant system is small, but it plays an important role in the various properties of the sealant. This article compares the effects of silane coupling agents KH-560 and KH-792 on the bonding properties, tensile modulus and elongation at break of one-component room temperature vulcanized silicone sealant. The results show:
1. For float glass, silane coupling agents with different ratios of KH-792 and KH-560 have little effect on the bonding performance of the sealant; for anodized aluminum, the dosage of KH-792 increases It can effectively improve the bonding performance of sealant.
2. The ratio of KH-792 and KH-560 has a greater impact on the mechanical properties of the sealant. As the amount of KH-792 increases, the fracture elongation of the sealant increases. The length gradually increased, while the tensile modulus showed a trend of increasing first and then leveling off.
